Merge pull request schmittjoh#780 from bblue/patch-1

Updated documentation related to PR schmittjoh#778

doc/cookbook/exclusion_strategies.rst

@@ -309,3 +309,22 @@ To enable this feature you have to set the Expression Evaluator when initializin
         ->build();
 
 .. _symfony expression language: https://github.com/symfony/expression-language
+
+By default the serializer exposes three variables (`object`, `context` and `property_metadata` for use in an expression. This enables you to create custom exclusion strategies similar to i.e. the [GroupExclusionStrategy](https://github.com/schmittjoh/serializer/blob/master/src/Exclusion/GroupsExclusionStrategy.php). In the below example, `someMethod` would receive all three variables.
+
+.. code-block :: php
+
+        <?php
+
+    class MyObject
+    {
+        /**
+         * @Exclude(if="someMethod(object, context, property_metadata)")
+         */
+        private $name;
+
+       /**
+         * @Exclude(if="someMethod(object, context, property_metadata)")
+         */
+        private $name2;
+    }